Method and apparatus for providing broadcast messages in a communications network

ABSTRACT

The present invention is a novel and improved method for providing broadcast short message services (SMS) in a communication network. It is an objective of the present invention to provide a method and apparatus that insures the successful transmission of the broadcast message while minimizing the impact of providing the short messaging service on overall system capacity. It is further the objective of the present invention to provide a method and apparatus for receiving broadcast messages without depriving the receiver of the benefits of slotted paging, that being the savings in power consumption.

This is a Continuation of application Ser. No. 08/316,157 filed Sep. 30,1994 now abandoned.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates to communications. More particularly, thepresent invention relates to a novel and improved method and apparatusfor providing broadcast short message services.

II. Description of the Related Art

In communication systems, a central communications center transmits datato remote subscriber stations. In order to efficiently use a limitedcommunications resource, the communications resource is divided intosub-bands and channels. A typical allocation of channels would include apilot channel, a synchronization channel providing necessary timinginformation, a plurality of traffic channels for conducting point topoint communications and a plurality of paging channels associated withthe traffic channels for providing signaling data.

Typically, when a subscriber station registers with the centralcommunications center, the central communications center informs thesubscriber station which paging channel of the plurality of availablepaging channels to monitor. When the central communications center needsto set up a point to point communication with a subscriber station ittransmits a traffic page on the paging channel being monitored by thesubscriber station. The traffic page would typically comprise subscriberstation identification information and traffic channel identificationinformation. In response to the received traffic page, the identifiedsubscriber station would prepare to conduct point to pointcommunications on the identified traffic channel.

Power consumption is an important consideration of the subscriberstations, particularly in the case of mobile subscriber stations. Inorder to reduce the power consumption of the subscriber stations, amethod known as slotted paging was devised. Slotted paging in a spreadspectrum communications system is described in detail in copending U.S.Pat. No. 5,392,287, assigned to assignee of the present invention andincorporated by reference herein. By this technique a subscriber stationmonitors its assigned paging channel at predetermined intervals, whichresults in a significant power savings relative to monitoring the pagingchannel continuously.

The central communications center must know a priori the time slots whenthe subscriber station will monitor the paging channel, and must reserveall pages for that subscriber station for these slots. When the pagingchannel is monitored at intervals, the system is referred to as slottedpaging, whereas when the paging channel is continuously monitored it isreferred to as non-slotted paging. The periods when the subscriberstation is not monitoring the paging channel can vary from subscriberstation to subscriber station depending on the needs of the subscriberstation user.

The expression slotted paging comes from dividing time into slots of apredetermined duration. In a slotted paging system, the subscriberstation monitors a slot, it will again monitor a subsequent slot anintegral number slots in the future. The number of slots betweenperiodically monitored slots is referred to as the slot cycle.

In addition, it is possible to send very short messages over the pagingchannel to subscriber stations. It is, however, important to keep thelength of such messages to a minimum because the paging channel resourceis a shared resource and by its nature scarce.

In the communications industry there is a need to be able to transmitbroadcast messages. Broadcast messages are messages that are provided toall users in a local area. For example a weather service, may provideweather forecasts to all the subscriber stations in a given area. Theuse of slotted paging provides a challenge to providing broadcastmessage in such a way that they can be received by all of the subscriberstations in the area.

SUMMARY OF THE INVENTION

The present invention is a novel and improved method for providingbroadcast short message services (SMS) in a communication network. It isan objective of the present invention to provide a method and apparatusthat insures the successful transmission of the broadcast message whileminimizing the impact of providing the short messaging service onoverall system capacity. It is further the objective of the presentinvention to provide a method and apparatus for receiving broadcastmessages without depriving the receiver of the benefit of reduced powerconsumption gained by slotted paging.

It is an advantage of the present invention that it is capable ofsuccessfully providing a broadcast short message service incommunication systems that provide for slotted paging and it is anadvantage of the present invention that it is capable of operation incommunication systems that support any number of paging channels.

In a first embodiment of the present invention, a broadcast message isprovided on every paging channel and in every slot in a predeterminedmaximum slot cycle. This message reaches all subscriber stationsregardless of its individual slot cycle or assigned paging channel. Thismessage contains a header that provides the subscriber station withinformation upon which to discriminate between broadcast messages thesubscriber station wishes to receive and broadcast messages thesubscriber station does not wish to receive.

In a second embodiment, a broadcast page is provided on every pagingchannel and in every slot in a predetermined maximum slot cycle. Thebroadcast page advertises a forthcoming broadcast message to allsubscriber stations. The corresponding broadcast message is providedonce on all paging channels and if the subscriber station wishes toreceive the broadcast message it monitors the paging channel at theappropriate time. The broadcast page may either explicitly indicate asingle slot position in which the corresponding broadcast message willbe provided or the slot position in which the corresponding broadcastmessage will be provided may be determined in accordance with adeterministic algorithm.

The third embodiment of the present invention provides for periodicbroadcast paging on all paging channels. In the third embodiment, allbroadcast pages are provided in one or more slots in a periodic cycle.The period of the broadcast paging slots is referred to as the broadcastcycle. As described above, the broadcast page may either explicitlyindicate a single slot position in which the corresponding broadcastmessage will be provided or the slot position in which the correspondingbroadcast message will be provided may be calculated using apredetermined convention. If the subscriber station wishes to receivebroadcast messages it must monitor its assigned paging channel duringthe broadcast page slot and then the subscriber station must monitor thepaging channel during the appropriate broadcast message slot in order toreceive the corresponding broadcast message.

The fourth embodiment of the present invention provides for singlechannel periodic broadcast paging. In the fourth embodiment, broadcastpages are provided periodically on a single designated paging channel.If a subscriber station wishes to receive broadcast messages, it tunesto the designated paging channel at the appropriate time to receive thebroadcast pages. If the subscriber station wishes to receive any of thecorresponding broadcast messages, the subscriber station tunes to thebroadcast message paging channel at the appropriate broadcast messageslot to receive the broadcast message. The broadcast message pagingchannel can be provided explicitly in the broadcast page or determinedin accordance with a predetermined convention.

In a preferred embodiment, the broadcast pages and broadcast messagesare provided redundantly with a temporal relationship to one anothersuch that all subscriber stations are able to receive a broadcast pageand its corresponding broadcast message. A method for determining theoptimal temporal relationship is described in detail herein.

The fifth embodiment operates in conjunction with the periodic broadcastpaging methods described previously. In the fifth embodiment, a new pageindicator is provided on every slot on every paging channel. This newpage indicator indicates to the subscriber station whether any newbroadcast pages will be provided in the periodic broadcast page slotsaving the subscriber station from monitoring the broadcast page slotwhen there are no new broadcast messages.

The sixth embodiment of the present invention operates in conjunctionwith methods in which broadcast pages advertise forthcoming broadcastmessages. In the exemplary embodiment, the broadcast page provides adelivery vector which indicates how the corresponding broadcast messageis to be received. In the exemplary embodiment, the delivery vectorselectively specifies a frequency sub-band, a channel and a time slot inwhich a corresponding broadcast message is to be provided. Furthermore,the broadcast page contains a broadcast handle that specifies the natureof the corresponding broadcast message. This broadcast message maycontain information as to the source of the message, the function of themessage, the language in which the message is provided and a sequencenumber. The broadcast handle provides sufficient information to allowthe subscriber station to determine whether or not to receive therelated broadcast message. In particular, the sequence number allows thesubscriber station to ignore duplicates thus providing a power savingsby avoiding the reception of broadcast messages already received.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objects, and advantages of the present invention willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout and wherein:

FIG. 1 is an illustration of the environment of the present invention;

FIG. 2 is an illustration of a division of a communication resource inthe exemplary embodiment of a spread spectrum multiple accesscommunication system;

FIG. 3 is a block diagram of the transmission system of the presentinvention; and

FIG. 4 is a block diagram of the receiving system of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, paging service providers 2, 4 and 6 providemessages to central communications center 10. The messages contain aheader indicating the nature of the message and the actual message to bebroadcast to the subscriber stations in the area. The broadcast messagesare then broadcast by central communication center 10 to subscriberstations 12, 14 and 16. Subscriber stations 12, 14 and 16 receive thebroadcast messages and selectively provide the messages to thesubscriber station user. In the exemplary embodiment, the signals aretransmitted by the central communication center 10 to subscriberstations 12, 14 and 16 in accordance with a CDMA communication format asdetailed in the U.S. Pat. Nos. 4,901,307 and 5,103,459, both assigned tothe assignee of the present invention.

Paging service providers 2, 4 and 6 may be commercial or governmentalservices that provide broadcast messages to users in the local area. Atypical example of paging service providers include services thatprovide stock quote or weather information. Broadcast messages may alsobe provided by private parties through general network 8. A typicalexample of this would be the case where an employer wishes to provide ashort message to its employees in the area.

FIG. 2 illustrates the exemplary method of dividing a communicationsresource, namely an allocated frequency band. In the exemplaryembodiment, the spectrum is divided into bands with the different bandsbeing used by different service providers. For example, the spectrum maybe divided into two halves as illustrated in FIG. 2, with a first halfof the spectrum being used by carrier A and the second half being usedby carrier B.

A carrier may then divide its portion of the overall spectrum intousable sub-bands. In FIG. 2, carrier A has divided its band of thespectrum into k separate sub-bands. In the exemplary embodiment, each ofthese sub-bands is then subdivided into channels, which are designatedaccording to their use. In FIG. 2, CDMA FREQUENCY 3 is illustrated asbeing subdivided into a pilot channel, a synchronization channel, mtraffic channels and n paging channels. It may be noted that it is notnecessary for each sub-band to contain all of the channels illustrated.In the exemplary embodiment of a CDMA communication system, the channelsare separated from one another in code space.

The traffic channels are used for point to point communications of dataand are allocated to an individual user for the duration of the point topoint service being provided. The paging channels are a set of commonlyshared channels used by the all of the subscriber stations for receivingsignaling and short message data. An example of signalling data is atraffic page instructing a subscriber station that point to pointcommunications are to be conducted and upon which traffic channel theyare to be conducted. The use of paging channels is described in detailthe aforementioned copending U.S. Pat. No. 5,392,287.

When a communication system uses a plurality of paging channels, eachuser is assigned a paging channel on which to receive pages. Asubscriber station monitors its assigned paging channel for trafficpages. In a non-slotted paging communication system the subscriberstation continuously monitors its assigned paging channel for pages.However, because constant monitoring entails excessive energyexpenditure, slotted paging communication systems were developed and aredescribed in detail in the aforementioned copending U.S. Pat. No.5,392,287.

In a slotted paging system, the subscriber station "wakes up" or "powersup" at predetermined time intervals, referred to as slot cycles, tomonitor its assigned paging channel for traffic pages. The centralcommunications center knows the times at which the subscriber stationwill be monitoring its assigned paging channel and in accordance withthis knowledge provides pages at such times that they may be received.

Different subscriber stations may monitor their assigned paging channelsat different slot cycles. In addition, in order to maximize systemcapacity, slotted paging systems distribute the slots in which differentsubscriber stations receive pages as uniformly as possible over apredetermined maximum slot cycle. The maximum slot cycle refers to thenumber of slots within which all subscriber stations must monitor theirassigned paging channels for incoming traffic pages. The varying slotcycles and the distribution of monitored slots over the maximum slotcycle pose challenges to broadcast paging, because it is rarely the casewhen all the users in the area are simultaneously monitoring any onepaging channel.

The first embodiment of the present invention provides the broadcastmessage on every paging channel and in every slot in the maximum slotcycle.

Referring now to FIG. 3, a message to be broadcast comprising a messageand a header indicating the nature of the message is provided tobroadcast page and message generator 20. Broadcast page and messagegenerator 20 generates a broadcast message in accordance with apredetermined broadcast format.

The broadcast message is provided to broadcast message buffer 24. Inresponse to timing signals from page transmit controller 34, broadcastmessage buffer 24 provides the broadcast message to encoder 27. Pagetransmit controller 34 in accordance with a clock signal from timingelement 32 provides timing signals such that the broadcast message isprovided redundantly in every slot in the maximum slot cycle.

Encoder 27 encodes the broadcast message for the purposes of errordetection/correction or privacy. The encoded broadcast message isprovided by encoder 27 to modulator 26.

Modulator 26 modulates the encoded broadcast message on each pagingchannel in accordance with signals from page transmit controller 34.

In the exemplary embodiment, modulator 26 is a code division multipleaccess (CDMA) modulator, as detailed in the aforementioned U.S. Pat.Nos. 4,901,307 and 5,103,459. The modulated broadcast message data isprovide to transmitter (TMTR) 28, which upconverts and amplifies thesignal so as to provide the broadcast message data on all subbands inaccordance with a signal from page transmit controller 34. The amplifiedand upconverted signal is provided to antenna 30 and broadcast to allsubscriber stations in the area.

FIG. 4 illustrates the exemplary receiving system of the presentinvention. The signal transmitted from antenna 30 is received at antenna50 and provided to receiver (RCVR) 52, where it is downconverted andamplified. Page receive controller 62 in accordance with a clock signalfrom timing element 58 determines the appropriate slot times for thereceiving system to monitor its assigned paging channel. In this firstexemplary embodiment, the receiving system monitors its assigned pagingchannel once per slot cycle for traffic pages and broadcast messages.

At the appropriate slot time page receive controller 62 provides atiming signal to receiver 52 that causes the receiver to become activeand monitor its assigned paging channel. The received signal is providedto demodulator 54, where it is demodulated. In the exemplary embodiment,demodulator 54 is a CDMA demodulator as described in detail in U.S. Pat.Nos. 4,901,307 and 5,103,459. Demodulator 54 provides the demodulatedsignal to decoder 56. Decoder 56 decodes the demodulated signal andselectively provides the broadcast message to the subscriber stationuser.

In a second exemplary embodiment of the present invention, a broadcastpage giving notice of a forthcoming broadcast message is provided inevery slot on every paging channel. The corresponding broadcast messageis provided in one slot on every paging channel. The temporalrelationship between the broadcast page and its corresponding broadcastmessage may be explicitly provided in the broadcast page or it may bedetermined in accordance with a deterministic algorithm.

Referring to FIG. 3, a message to be broadcast comprising a message anda header indicating the nature of the message is provided to broadcastpage and message generator 20. Broadcast page and message generator 20generates a broadcast message and broadcast page in accordance with apredetermined broadcast format, for example a hashing algorithm.

In an exemplary hashing algorithm, assume that each broadcast pagecontains a broadcast handle that provides the subscriber station withinformation with which to determine the nature of the broadcast message.Then assume that there is a function H that maps the space of allbroadcast handles to a uniform distribution into the range0≦H(handle)<N, where N is value determined to provide an acceptabledistribution of the broadcast messages on the paging channel. If thebroadcast page is provided in slot b_(page), then the correspondingmessage will be provided in slot b_(msg) given by the value:

    b.sub.msg =b.sub.0 +H(handle),                             (1)

where b₀ is a fixed offset following the slot in which the last of thebroadcast pages for the broadcast message, b_(msg), occurs. In caseswhere the broadcast page is only provided once, b₀ is the slot in whichthe single broadcast page is provided.

In a preferred hashing algorithm, the central communications center isprovided with a means for deconflicting two messages that hash to thesame slot. In the preferred hashing algorithm the broadcast page isdelineated into two separate sub-fields, one is referred to as thesequence number, i, and the other is referred to as the identifier, x.If the broadcast page is provided in slot b_(page), then thecorresponding message will provided in slot b_(msg) given by the value:

    b.sub.msg =b.sub.0 +(H(x)+i)mod B,                         (2)

where b₀ is a fixed offset following the slot in which the last of thebroadcast page for the broadcast message, b_(msg), occurs, H(x) maps thespace of all identifiers to the range of 0≦H(x)<N and B is the broadcastcycle. In general the sequence numbers for two broadcast messagesprovided in the same broadcast cycle will be the same. However, in thecase that two broadcast messages hash to the same slot number, thecentral communications center can deconflict the broadcast messages bychanging the sequence number, i, of one of the messages.

The broadcast message is provided to broadcast message buffer 24 and thebroadcast page is provided to broadcast page buffer 22. Page transmitcontroller 34 provides timing signals to broadcast page buffer 22 suchthat the broadcast page is provided in each slot in the maximum slotcycle. In response to the timing signals from page transmit controller34, broadcast page buffer 22 provides the broadcast pages to encoder 27.Encoder 27 encodes the broadcast pages and provides the encodedbroadcast pages to modulator 26. Modulator 26 modulates the encodedbroadcast pages such that the broadcast pages are provided on everypaging channel in accordance with signals from page transmit controller34.

The modulated broadcast pages are provided by modulator 26 totransmitter (TMTR) 28, which upconverts and amplifies the signal so asto provide the broadcast pages on all paging channels in accordance witha signal from page transmit controller 34. The amplified and upconvertedbroadcast page signal is provided to antenna 30 and broadcast to allsubscriber stations in the local area.

After the broadcast pages for the entire maximum slot cycle have beentransmitted, page transmit controller 34 provides a timing signal at theappropriate broadcast message slot time to message buffer 24. Messagebuffer 24 provides the broadcast message to encoder 27 in accordancewith the timing signal. Encoder 27 encodes the broadcast message andprovides the encoded broadcast message to modulator 26.

Modulator 26 modulates the encoded broadcast message on each pagingchannel in accordance with signals from page transmit controller 34. Themodulated broadcast message is provided by modulator 26 to transmitter(TMTR) 28, which upconverts and amplifies the message so as to providethe broadcast message on all paging channels in accordance with a signalfrom page transmit controller 34. The amplified and upconvertedbroadcast message is provided to antenna 30 and broadcast to allsubscriber stations in the local area.

Referring to FIG. 4, page receive controller 62 provides a slot timingsignal to receiver 52 that causes receiver 52 to monitor its assignedpaging channel. The broadcast page is provided through antenna 50 toreceiver 52 where it is downconverted and amplified. The receivedbroadcast page is provided to demodulator 54, where it is demodulatedand provided to decoder 56.

Decoder 56 decodes the broadcast page and provides the decoded broadcastpage to page receive controller 62. Page receive controller 62determines in accordance with a predetermined set of user preferences ifthe forthcoming broadcast message will be of interest to the subscriberstation user.

If page receive controller 62 determines that the forthcoming broadcastmessage will be of interest to the subscriber station user, then itgenerates signals to receive the broadcast message. Page receivecontroller 62 determines the slot in which the broadcast message will beprovided. The slot containing the broadcast message may be extractedfrom the broadcast page or determined in accordance with a deterministicalgorithm.

Page receive controller 62 provides a slot timing signal to receiver 52that cause the receiver to monitor the paging channel at the timeappropriate for receiving the broadcast message. Receiver 52 receivesthe broadcast message provided through antenna 50 and downconverts andamplifies the received broadcast message. The received broadcast messageis then provided to demodulator 54 which demodulates the receivedbroadcast message. The demodulated broadcast message is provided todecoder 56 which decodes the broadcast message and provides thebroadcast message to the subscriber station user.

In a third exemplary embodiment, broadcast pages are providedperiodically in a designated slot on all paging channels. As describedpreviously, the broadcast pages provide information about forthcomingbroadcast messages. The corresponding broadcast messages are provided atleast once on every paging channel. The period at which the broadcastpages are provided is referred to as the broadcast cycle. If asubscriber station is to receive broadcast messages it must monitor itsassigned paging channel during the slot times in which broadcast pagesare provided.

Referring to FIG. 3, a message to be broadcast comprising a message anda header indicating the nature of the message is provided to broadcastpage and message generator 20. Broadcast page and message generator 20generates a broadcast message and broadcast page in accordance with apredetermined broadcast format.

The broadcast message is provided to broadcast message buffer 24 and thebroadcast page is provided to broadcast page buffer 22. Page transmitcontroller 34 provides a timing signal to broadcast page buffer 22 toprovide the broadcast page in the appropriate broadcast page slot. Inresponse to the timing signal from page transmit controller 34,broadcast page buffer 22 provides the broadcast page to encoder 27.Encoder 27 encodes the broadcast page and provides the encoded broadcastpage to modulator 26.

Modulator 26 modulates the encoded broadcast page so as to provide thebroadcast page on each paging channel in accordance with signals frompage transmit controller 34. The modulated broadcast page is provided bymodulator 26 to transmitter (TMTR) 28, which upconverts and amplifiesthe broadcast page signal so as to provide the broadcast page on allpaging channels in accordance with a signal from page transmitcontroller 34. The amplified and upconverted broadcast page signal isprovided to antenna 30 and broadcast to all subscriber stations in thelocal area.

In the transmission of the corresponding broadcast message, pagetransmit controller 34 provides a timing signal to broadcast messagebuffer 22 indicating the appropriate slot in which to provide thebroadcast message. In response, broadcast message buffer 22 provides thebroadcast message to encoder 27. Encoder 27 encodes the broadcastmessage and provides the encoded broadcast message to modulator 26.

Modulator 26 modulates the encoded broadcast message on each pagingchannel in accordance with signals from page transmit controller 34. Themodulated broadcast message is provided by modulator 26 to transmitter(TMTR) 28, which upconverts and amplifies the broadcast message toprovide the broadcast message on all paging channels in accordance witha signal from page transmit controller 34. The amplified and upconvertedbroadcast message signal is provided to antenna 30 and broadcast to allsubscriber stations in the local area.

Referring to FIG. 4, page receive controller 62 provides a slot timingsignal to receiver 52 that causes receiver 52 to monitor its assignedpaging channel during the broadcast page slot. The received broadcastpage is provided to demodulator 54, where it is demodulated and providedto decoder 56. Decoder 56 decodes the broadcast page signal and providesthe decoded broadcast page to page receive controller 62. Page receivecontroller 62 determines in accordance with a set of user preferences ifthe corresponding broadcast message will be of interest to thesubscriber station user.

If page receive controller 62 determines that the forthcoming broadcastmessage is of interest to the subscriber station user, then it generatessignals to receive the corresponding broadcast message. Page receivecontroller 62 determines the slot in which the broadcast message will beprovided. As described previously, the slot containing the broadcastmessage may be extracted from the broadcast page or determined by adeterministic algorithm.

Page receive controller 62 provides a slot timing signal to receiver 52that causes receiver 52 to monitor its paging channel at the timeappropriate for receiving the broadcast message. Receiver 52 receivesthe broadcast message provided through antenna 50 and downconverts andamplifies the received broadcast message and provides the signal todemodulator 54. Demodulator 54 demodulates the received broadcastmessage and provides the demodulated broadcast message to decoder 56which decodes the broadcast message and provides the broadcast messageto the subscriber station user.

In the fourth embodiment of the present invention, broadcast pages areprovided periodically on a single designated paging channel. In theexemplary embodiment, the corresponding broadcast messages are providedon the same designated paging channel. If a subscriber station is toreceive broadcast messages, it must tune to the designated pagingchannel at the appropriate slot time to receive the broadcast pages.

If the subscriber station wishes to receive a corresponding broadcastmessage it must tune to and monitor the designated paging channel at theappropriate broadcast message slot time. As described previously, thetemporal relationship between the broadcast page and correspondingbroadcast message may be explicitly provided in the broadcast page or itmay be determined by a deterministic relationship.

Referring to FIG. 3, a message to be broadcast comprising a message anda header indicating the nature of the message is provided to broadcastpage and message generator 20. Broadcast page and message generator 20generates a broadcast message and broadcast page in accordance with apredetermined broadcast format.

The broadcast message is provided to broadcast message buffer 24 and thebroadcast page is provided to broadcast page buffer 22. Page transmitcontroller 34 provides a timing signal to provide the broadcast page inthe appropriate slot. In response to the timing signal from pagetransmit controller 34, broadcast page buffer 22 provides the broadcastpage to encoder 27. Encoder 27 encodes the broadcast page and providesthe encoded broadcast page to modulator 26.

Modulator 26 provides the encoded broadcast page on the designatedpaging channel in accordance with a signal from page transmit controller34. The modulated broadcast page is provided by modulator 26 totransmitter (TMTR) 28, which upconverts and amplifies the broadcast pagesignal so as to provide the broadcast page on the designated pagingchannel in accordance with a signal from page transmit controller 34.The amplified and upconverted broadcast page signal is provided toantenna 30 and broadcast to all subscriber stations in the local area.

In the transmission of the corresponding broadcast message, pagetransmit controller 34 provides a timing signal to broadcast messagebuffer 22 indicating the appropriate slot in which to provide thebroadcast message. Broadcast message buffer 22 provides the broadcastmessage to encoder 27. Encoder 27 encodes the broadcast message andprovides the encoded broadcast message to modulator 26.

Modulator 26 modulates the encoded broadcast message on the designatedpaging channel in accordance with signals from page transmit controller34. The modulated broadcast message is provided by modulator 26 totransmitter (TMTR) 28, which upconverts and amplifies the signal toprovide the broadcast message on the designated paging channel inaccordance with a signal from page transmit controller 34. The amplifiedand upconverted broadcast message signal is provided to antenna 30 andbroadcast to all subscriber stations in the local area.

Referring to FIG. 4, page receive controller 62 provides a slot timingsignal to receiver 52 that causes receiver 52 to tune to and monitor thedesignated paging channel during the broadcast page slot. The broadcastpage is received through antenna 50 and downconverted and amplified byreceiver 52. Receiver 52 provides the broadcast page to demodulator 54,where it is demodulated and provided to decoder 56. Decoder 56 decodesthe broadcast page and provides the decoded broadcast page to pagereceive controller 62. Page receive controller 62 determines inaccordance with a set of user preferences if the corresponding broadcastmessage is of interest to the subscriber station user.

If page receive controller 62 determines that the forthcoming broadcastmessage is of interest to the subscriber station user, then it generatessignals to receive the corresponding broadcast message. Page receivecontroller 62 determines the slot in which the broadcast message will beprovided.

Page receive controller 62 provides a slot timing signal to receiver 52that causes receiver 52 to tune to and monitor the designated pagingchannel at the broadcast message slot time. Receiver 52 receives thebroadcast message provided through antenna 50 and downconverts andamplifies the received broadcast-message. Demodulator 54 demodulates thereceived broadcast message and provides the demodulated broadcastmessage to decoder 56 which decodes the broadcast message and providesthe broadcast message to the subscriber station user.

In a preferred embodiment of the fourth embodiment, the broadcast pageand broadcast message data are each provided twice in order to insurethat two consecutive broadcast paging slots or any two consecutivetransmissions of a broadcast message do not both coincide with thetraffic paging slots of any subscriber station. Subscriber stations inthe system may be assigned a slot cycle of a specified period, S_(n).Each subscriber station is able to choose its slot cycle from a range ofslot cycles, S₁, S₂, . . . . For an arbitrary subscriber unit, x, havinga traffic slot cycle of S_(n), its paging slots, s_(n), will occuraccording to:

    s.sub.n =(n*S.sub.n)+F(x),                                 (3)

where F(x) uniformly maps a subscriber's unique station identifier tothe range 0≦F(x)<S_(n).

The system may also specify a broadcast paging slot cycle having periodB where at least one slot of every broadcast cycle is used to transmitbroadcast pages. In such a system, it may be desirable to choosebroadcast paging slots in such a way that no two consecutive broadcastpaging slots both coincide with the traffic paging slot of an arbitrarysubscriber. This can be done by choosing consecutive paging slots suchthat the distance between them, in slots, is not evenly divisible by anytraffic slot cycle S_(n) that is available to subscriber stations.

In the exemplary embodiment, subscriber stations are able to choose froma set of traffic paging cycles having period as specified by:

    S.sub.n =2.sup.n *16,(0≦n≦7)                 (4)

Let the broadcast paging cycle period for all subscriber stations bespecified by:

    B=2.sup.m *16,(0≦m≦7)                        (5)

Let b_(k) represent a slot number relative to the beginning of broadcastcycle k. Then let succeeding broadcast page slots be defined by thefollowing recurrence relation.

    b.sub.k =(b.sub.k-1 +i)mod B.                              (6)

Note that any value of i, 1≦i≦15 will produce broadcast paging slotshaving the desired property of non-coincidence with traffic pagingslots. However, in a variation on the embodiment mentioned above,subscriber stations may actually monitor the slot immediately precedingand immediately following their assigned slots, thus restricting thevalue of i such that 2≦i≦14. Also note that it may be desirable to picka value of i such that the distance between two broadcast pages, both ofwhich may coincide with the traffic paging slot of some subscriber unit,is maximized. A value of i=3 has this property and is the value selectedfor the exemplary embodiment. In fact, any value of i which is less thanand relatively prime to the least common factor of B and S_(n) has thisproperty. To insure that two consecutive pages P_(k) and P_(k+1) do notboth coincide with the traffic slots of an arbitrary subscriber station,the difference (P_(k+1) -P_(k)) must not be divisible by S_(n).

In a first method to deconflict traffic and broadcast slots, a firstbroadcast page is transmitted advertising two forthcoming broadcastmessages, then a second broadcast page is transmitted advertising thesame two forthcoming broadcast messages. If as described above the twobroadcast pages are separated by a broadcast cycle plus a number ofslots that is less than and relatively prime to the least common factorof B and S_(n), then all subscriber stations can receive one or theother of the two broadcast pages.

If in addition the two redundantly provided broadcast messages aresimilarly separated by a broadcast cycle plus a number of slots that isless than and relatively prime to the least common factor of B andS_(n), then all subscriber stations can receive one or the other of thetwo broadcast messages. The positions of the broadcast messages can beprovided explicitly in the broadcast pages or the number of slotsbetween the second broadcast page and the first corresponding broadcastmessage can be determined in accordance with the hashing algorithmsdescribed previously. It should be noted that providing more than onebroadcast page or message in a given broadcast cycle may result in anunacceptable distribution, which can be fixed by the additional offsetof a broadcast cycle provided between any of the broadcast pages ormessages.

In a second method to deconflict traffic and broadcast slots, a firstbroadcast page is transmitted advertising a forthcoming broadcastmessage, then a second broadcast page is transmitted advertising thesame forthcoming duplicate broadcast message. In this method the twobroadcast pages are separated by a broadcast cycle plus a number ofslots that is less than and relatively prime to the least common factorof B and S_(n). The relationship between the broadcast page and itscorresponding broadcast message must be equal to an integral multiple ofthe least common multiple of the possible slot cycles.

The fifth exemplary embodiment operates in conjunction with any of themethods described previously for periodic broadcast paging. In the fifthembodiment, the transmission system provides a new page indicator ineach slot in a maximum slot cycle and on every paging channel. When asubscriber station monitors its paging channel for traffic pages, it candetermine from the new page indicator if it needs to monitor for newbroadcast pages. This can result in a power savings for the subscriberstation, in that it will not unnecessarily monitor for incomingbroadcast pages. This exemplary embodiment operates in conjunction withthe second third or fourth exemplary embodiments.

In the exemplary embodiment, the broadcast page consists essentially oftwo fields. The first field referred to as the broadcast handle is usedby the subscriber station to discriminate between those messages that itwishes to receive and those that it does not. The second field isreferred to as the delivery vector and as described previously tells thesubscriber station to which channel and sub-band to tune and in whichslot to receive the corresponding broadcast message.

The broadcast handle consists optionally of four sub-fields. Thesub-fields include source address, function code, sequence number andlanguage indicator. The source address identifies the sender of themessage. he function code indicates the subject matter of the message.The sequence number identifies the version of the message, so that inthe case where the broadcast page is provided redundantly, thesubscriber station will be able to avoid receiving the same messagetwice. The language indicator indicates the language in which themessage is provided (i.e. English, Spanish, French, etc.). It is notnecessary for each sub-field to be uniquely specified as long as theaggregate broadcast handle is uniquely specified. It is, also, notnecessary to provide information in all of the sub-fields.

The delivery vector consists of three sub-fields which in the exemplaryembodiment included frequency band, channel and slot sub-fields. Thefrequency band sub-field specifies the frequency sub-band in which thecorresponding broadcast message will be provided. The channel sub-fieldspecifies the paging or traffic channel where the correspondingbroadcast message will be provided. The slot sub-field specifies theslot number within the specified sub-band and channel where thebroadcast messages will be provided. As described previously any or allof the delivery vector sub-fields can be provided explicitly ordetermined in accordance with a predetermined calculation format.

It may be desirable to provide paging using a combination of theabovementioned techniques. For example it may be desirable to employ amore efficient broadcast paging method in general situations, but toprovide an explicit page on all slots in a broadcast cycle in the eventof an emergency message.

The previous description of the preferred embodiments is provided toenable any person skilled in the art to make or use the presentinvention. The various modifications to these embodiments will bereadily apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other embodiments without the use ofthe inventive faculty. Thus, the present invention is not intended to belimited to the embodiments shown herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

We claim:
 1. An apparatus for receiving broadcast messages from atransmitter in a communication network, said network having multiplepaging channels, wherein each of said multiple paging channels isdivided into predetermined slot cycles, wherein each of saidpredetermined slot cycles is divided into time slots, said networkfurther containing multiple receivers, wherein each of said multiplereceivers monitors an assigned paging channel of said multiple pagingchannels and an assigned time slot within each slot cycle, saidapparatus comprising:page receive controller means for providing atiming signal indicative of said assigned time slot within each of saidslot cycles; receiver means for monitoring said assigned paging channelin a single time slot of said slot cycle in accordance with said timingsignal and for receiving said broadcast message during said single timeslot; and decoder means for decoding said broadcast message and forselectively processing said broadcast message in accordance with apredetermined set of user preferences.
 2. An apparatus for transmittingbroadcast messages to a plurality of receivers in a communicationnetwork, said network having multiple paging channels, wherein each ofsaid multiple paging channels is divided into predetermined slot cycles,wherein each of said predetermined slot cycles is divided into timeslots, said network further containing multiple receivers, wherein eachof said multiple receivers monitors an assigned one of said multiplepaging channels at a first assigned one of said time slots within afirst slot cycle for receiving traffic pages and a second one of saidtime slots within said first slot cycle, said second one of said timeslots designated as a broadcast page time slot, and wherein saidbroadcast message is received on said assigned one of said pagingchannels at a third time slot within a second slot cycle, said apparatuscomprising:page transmit controller means for providing a page timingsignal indicative of said broadcast page time slot within said firstslot cycle and for providing a broadcast message timing signalindicative of said third time slot within said second slot cycle;broadcast page buffer means for providing a broadcast page in accordancewith said page timing signal; message buffer means for providing saidbroadcast message in accordance with said broadcast message timingsignal; modulator means for providing said broadcast page on each ofsaid multiple paging channels and for providing said broadcast messageon each of said multiple paging channels; and transmitter means fortransmitting said broadcast page and said broadcast message.
 3. Theapparatus of claim 2 wherein:said page transmit controller means isfurther for providing a new page timing signal indicative of a new pageindicator in each time slot of said first slot cycle, wherein said newpage indicator indicates whether or not a new broadcast page isavailable to be received; said broadcast page buffer means is furtherfor providing said new page indicator in accordance with said new pagetiming signal; said modulator means is further for providing said newpage indicator upon each of said multiple paging channels; and saidtransmitter means is further for transmitting said new page indicator.4. An apparatus for receiving broadcast messages from a transmitter in acommunication network, said network having multiple paging channels,wherein each of said multiple paging channels is divided intopredetermined slot cycles, wherein each of said predetermined slotcycles is divided into time slots, said network further containingmultiple receivers, wherein each of said multiple receivers monitors anassigned one of said multiple paging channels at a first assigned one ofsaid time slots within a first slot cycle for receiving traffic pagesand a second one of said time slots within said first slot cycle, saidsecond one of said time slots designated as a broadcast page time slot,and wherein said broadcast message is received on said assigned one ofsaid paging channels at a third time slot within a second slot cycle,said apparatus comprising:page receive controller means for providing apage timing signal indicative of said broadcast page time slot withineach slot cycle and for determining in which time slot a broadcastmessage may be received; receiver means for monitoring said assigned oneof said multiple paging channels in accordance with said page timingsignal and for receiving a broadcast page, wherein said broadcast pagespecifies said third time slot within said second slot cycle; decodermeans for decoding said broadcast page and for providing said decodedbroadcast page to said page receive controller, wherein said pagereceive controller is further for determining in accordance with apredetermined set of user preferences, whether to receive said broadcastmessage; broadcast message controller means for providing a broadcastmessage timing signal indicative of said third time slot within saidsecond slot cycle; and broadcast message receiver means for receivingsaid broadcast message in accordance with said broadcast message timingsignal.
 5. The apparatus of claim 4 wherein:said page receive controllermeans is further for providing a new page timing signal indicative of anew page indicator at said first assigned one of said time slots in eachslot cycle, wherein said new page indicator indicates whether or not anew broadcast page is available to be received; said receiving means isfurther for receiving said new page indicator; and said decoder means isfurther for preventing said receiver means from monitoring said one ofsaid assigned paging channels for said broadcast page if said new pageindicator indicates that no broadcast page is available to be received.6. An apparatus for transmitting broadcast messages to a plurality ofreceivers in a communications network, said network having multiplepaging channels, wherein each of said multiple paging channels isdivided into predetermined slot cycles, wherein each of saidpredetermined slot cycles is divided into time slots, said networkfurther containing multiple receivers, wherein each of said multiplereceivers monitors an assigned one of said multiple paging channels at afirst assigned one of said time slots within a first slot cycle forreceiving traffic pages and a second paging channel, designated as abroadcast message paging channel where broadcast pages and saidbroadcast messages are transmitted on, at a second one of said timeslots within a second slot cycle, and wherein said broadcast message isreceived on said broadcast message paging channel at a third time slotwithin said second slot cycle, said apparatus comprising:page transmitcontroller means for providing a page timing signal indicative of saidsecond time slot within said second slot cycle and for providing abroadcast message timing signal indicative of said third time slotwithin said second slot cycle; broadcast page buffer means for providinga broadcast page in accordance with said page timing signal, whereinsaid broadcast page specifies said third time slot within said secondslot cycle; broadcast message buffer means for providing said broadcastmessage in accordance with said broadcast message timing signal;modulator means for providing said broadcast page upon said broadcastmessage paging channel and for providing said broadcast message on saidbroadcast message paging channel; and transmitter means for transmittingsaid broadcast page and said broadcast message.
 7. The apparatus ofclaim 6 wherein:said page transmit controller means is further forproviding a new page timing signal indicative of a new page indicator ineach time slot of said first slot cycle, and wherein said new pageindicator indicates whether or not a new broadcast page is available tobe received; said broadcast page buffer means is further for providingsaid new page indicator in accordance with said new page timing signal;said modulator means is further for providing said new page indicatorupon each of said multiple paging channels; and said transmitter meansis further for transmitting said new page indicator.
 8. An apparatus forreceiving broadcast messages from a transmitter in a communicationsnetwork, said network having multiple paging channels, wherein each ofsaid multiple paging channels is divided into predetermined slot cycles,wherein each of said predetermined slot cycles is divided into timeslots, said network further containing multiple receivers, wherein eachof said multiple receivers monitors an assigned one of said multiplepaging channels at a first assigned one of said time slots within afirst slot cycle for receiving traffic pages and a second pagingchannel, designated as a broadcast message paging channel wherebroadcast pages and said broadcast messages are transmitted on, at asecond time slot within a second slot cycle, and wherein said broadcastmessage is received on said broadcast message paging channel at a thirdtime slot within said second slot cycle, said apparatus comprising:pagereceive controller means for providing a page timing signal indicativeof said second time slot within each slot cycle, and for determining inwhich time slot a broadcast message may be received; broadcast messagecontroller means for providing a broadcast message timing signalindicative of said third time slot within said second slot cycle;receiver means for monitoring said broadcast message paging channel inaccordance with said page timing signal, for receiving said broadcastpage, for monitoring said broadcast message paging channel in accordancewith said broadcast message timing signal, and for receiving saidbroadcast message; and decoder means for decoding said broadcast pageand for providing said decoded broadcast page to said page receivecontroller, wherein said page receive controller is further fordetermining in accordance with a predetermined set of user preferences,whether to receive said broadcast message.
 9. The apparatus of claim 8wherein:said page receive controller means is further for providing anew page timing signal indicative of a new page indicator at said firstassigned one of said time slots in each slot cycle, and wherein said newpage indicator indicates whether or not a new broadcast page isavailable to be received; said receiving means is further for receivingsaid new page indicator; and said decoder means is further forpreventing said receiver means from monitoring said one of said assignedpaging channels for said broadcast page if said new page indicatorindicates that no broadcast page is available to be received.
 10. Anapparatus for receiving broadcast messages from a transmitter in acommunication network, said network having multiple paging channels,wherein each of said multiple paging channels is divided intopredetermined slot cycles, wherein each of said predetermined slotcycles is divided into time slots, said network further containingmultiple receivers, wherein each of said multiple receivers monitors afirst paging channel at each time slot within a first slot cycle and asecond paging channel, designated as a broadcast message paging channelwhere broadcast pages and said broadcast messages are received, at asecond time slot within a second slot cycle, and wherein said broadcastmessage is received on said broadcast message paging channel at a thirdtime slot within either said second slot cycle or a third slot cycle,said apparatus comprising:page receive controller means for providing afirst page timing signal indicative of each time slot within said firstslot cycle, for providing a second page timing signal indicative of saidsecond time slot within said second slot cycle, and for providing abroadcast message timing signal indicative of said third time slotwithin either said second slot cycle or said third slot cycle; pagereceiver means for monitoring said first paging channel in accordancewith said first page timing signal, for receiving a first broadcastpage, for monitoring said broadcast message paging channel in accordancewith said second page timing signal, for receiving a second broadcastpage, for monitoring said broadcast message paging channel in accordancewith said broadcast message timing signal, and for receiving a broadcastmessage; and decoder means for decoding said first broadcast page, forproviding said decoded first broadcast page to said page receivecontroller, for decoding said second broadcast page, and for providingsaid decoded second broadcast page to said page receive controller,wherein said page receive controller is further for determining whethersaid second broadcast page is available to be received on said broadcastmessage paging channel and for determining in accordance with apredetermined set of user preferences, whether to receive said broadcastmessage.
 11. An apparatus for transmitting broadcast messages to aplurality of receivers in a communications network, said network havingmultiple paging channels, wherein each of said multiple paging channelsis divided into predetermined slot cycles, wherein each of saidpredetermined slot cycles is divided into time slots, said networkfurther containing multiple receivers, wherein each of said multiplereceivers monitors a first paging channel at each time slot within afirst slot cycle and a second paging channel, designated as a broadcastmessage paging channel where broadcast pages and said broadcast messagesare transmitted on, at a second time slot within a second slot cycle,and wherein said broadcast message is received on said broadcast messagepaging channel at a third time slot within either said second slot cycleor a third slot cycle, said apparatus comprising:page transmitcontroller means for providing a first page timing signal indicative ofall time slots of said first slot cycle, for providing a second pagetiming signal indicative of a second time slot in a second slot cycle,and for providing a broadcast message timing signal indicative of saidthird time slot in either said second slot cycle or said third slotcycle; page buffer means for providing a first broadcast page inaccordance with said first page timing signal, wherein said firstbroadcast page indicates whether or not a second broadcast page is to betransmitted on said second paging channel, and for providing a secondbroadcast page in accordance with said second page timing signal,wherein said second broadcast page indicates said broadcast messagetiming information; message buffer means for providing said broadcastmessage in accordance with said broadcast message timing signal;modulator means for providing said first broadcast page upon everypaging channel, for providing said second broadcast page on saidbroadcast message paging channel, and for providing said broadcastmessage on said broadcast message paging channel; and transmitter meansfor transmitting said first broadcast page, said second broadcast page,and said broadcast message.
 12. The apparatus of claim 11 wherein saidsecond broadcast page comprises:a broadcast handle which identifies thecontent of said broadcast message; and a delivery vector whichidentifies where to receive said broadcast message.
 13. The apparatus ofclaim 12 wherein said broadcast handle comprises:a source address whichidentifies the sender of said broadcast message.
 14. The apparatus ofclaim 13 wherein said broadcast handle further comprises:a function codewhich indicates the subject matter of the message.
 15. The apparatus ofclaim 14 wherein said broadcast handle further comprises:a sequencenumber which identifies the version number of said broadcast messagesuch that each of said plurality of receivers can avoid receiving thesame broadcast message twice.
 16. The apparatus of claim 15 wherein saidbroadcast handle further comprises:a language indicator which indicateswhich the language in which the message is provided.
 17. The apparatusof claim 12 wherein said delivery vector comprises:a frequency bandsub-field which identifies on which frequency sub-band said broadcastmessage will be transmitted.
 18. The apparatus of claim 17 wherein saidfrequency sub-field is indicated within said second broadcast page. 19.The apparatus of claim 17 wherein said frequency sub-field is determinedin accordance with a predetermined calculation format.
 20. The apparatusof claim 17 wherein said delivery vector further comprises:a channelsub-field which identifies on which channel said broadcast message willbe transmitted.
 21. The apparatus of claim 20 wherein said deliveryvector further comprises:a slot sub-field which identifies in which timeslot said broadcast message will be transmitted.
 22. The apparatus ofclaim 21 wherein said slot sub-field is indicated within said secondbroadcast page.
 23. The apparatus of claim 21 wherein said slotsub-field is determined in accordance with a predetermined calculationformat.
 24. The apparatus of claim 20 wherein said channel sub-field isindicated within said second broadcast page.
 25. The apparatus of claim20 wherein said channel sub-field is determined in accordance with apredetermined calculation format.